Method of forming a multi-layer plastic pipe for conducting fluids

Abstract

A method of forming a two-layer plastic pipe (4;8) to be laid in the ground for conducting material therethrough forms a core pipe (2) consisting essentially of a first plastic material and forms a detachable outer hose (3;7) of a second plastic material around said core pipe (2) by a suitable coating method, including in said second plastic material an amount of additives effective to protect said core pipe with said outer hose from stresses and loads of laying said core pipe and outer hose and usage thereof in ground.

We claim: 
     
       1. A method of forming a two-layer plastic pipe to be laid in the ground for conducting material therethrough, the method comprising the step of: forming a core pipe (2) consisting essentially of a first plastic material substantially free from colouring and stabilizing agents;   forming a detachable outer hose (3;7) of a second plastic material around said core pipe (2) by a suitable coating method and including in said second plastic material an amount of additives effective to protect said core pipe with said outer hose from stresses and loads of laying said core pipe and outer hose and usage thereof in ground; and   providing a release layer between said core pipe and said outer hose for making said outer hose more easily detachable from said core pipe than without said release layer.   
     
     
       2. In a method of forming a two-layer plastic pipe laid in the ground for conducting material therethrough, the improvement of the method comprising the step of: forming a core pipe (2) consisting essentially of a first plastic material;   forming a detachable outer hose (3;7) of a second plastic material around said core pipe (2) by a suitable coating method and including only in said second plastic material an amount of additives effective to protect said core pipe with said outer hose from stresses and loads of laying said core pipe and outer hose and usage thereof in ground; and   providing a release layer between said core pipe and said outer hose for making said outer hose more easily detachable from said core pipe than without said release layer.   
     
     
       3. A method according to claim 1, wherein said release layer between the core pipe and the outer hose (3) comprises a layer of wax. 
     
     
       4. A method according to claim 1, wherein said release layer between the core pipe and the outer hose (3) comprises a thin aluminum layer. 
     
     
       5. A method according to claim 1, wherein the plastic material of said outer hose is formed on the core pipe in a non-adherent state to render it easily detachable from the core pipe. 
     
     
       6. A method according to claim 5, wherein said non-adherent state of the outer hose is achieved by adding wax as a release agent to the plastic material of the outer hose (3). 
     
     
       7. A method according to claim 5, wherein said non-adherent state of the outer hose is achieved by adding chalk as a release agent to the plastic material of the outer hose (3). 
     
     
       8. A method according to claim 5, wherein said non-adherent state of the outer hose is achieved by adding talc as a release agent to the plastic material of the outer hose (3). 
     
     
       9. A method according to claim 5, wherein said non-adherent state of the outer hose is achieved by cooling the plastic material of the outer hose (3) before forming it on the core pipe. 
     
     
       10. A method according to claim 1, wherein the outer hose (3) is provided around the core pipe (2) by coextrusion. 
     
     
       11. A method according to claim 1, comprising the step of mixing flake-like mica with the plastic material of the outer hose (3). 
     
     
       12. A method according to claim 1, comprising the step of mixing reinforced fibres with the plastic material of the outer hose (3). 
     
     
       13. A method according to claim 1, comprising the step of forming flanges or corrugations (6) spaced from one another on the outer hose (7). 
     
     
       14. A method according to claim 1, comprising the step of foaming the plastic material of the outer hose (3). 
     
     
       15. A method according to claim 1, comprising the step of crosslinking the plastic material of the outer hose (3). 
     
     
       16. A method according to claim 1, comprising the step of mixing identifying dyes and UV stabilizing agents with the plastic material of the outer hose (3).